Integrated compound nano probe card and method of making same

ABSTRACT

An integrated compound nano probe card is disclosed to include a substrate layer having a front side and a back side, and compound probe pins arranged in the substrate layer. Each compound probe pin has a bundle of aligned parallel nanotubes/nanorods and a bonding material bonded to the bundle of aligned parallel nanotubes/nanorods and filled in gaps in the nanotubes/nanorods. Each compound probe pin has a base end exposed on the back side of the substrate layer and a distal end spaced above the front side of the substrate layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of patent application Ser. No.10/393,262 filed Mar. 21, 2003 now U.S. Pat. No. 7,400,159 B2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a probe card for testingelectronic elements and its fabrication method and, more specifically,to an integrated compound nano probe card. The invention relates also tothe fabrication of the integrated compound nano probe card.

2. Description of the Related Art

A variety of probe cards for testing electrical properties of anelectronic element are commercially available. These probe cards includetwo types, i.e., the cantilever type and the vertical type. The probepins of these two types of probe cards are tungsten pins, lead pins, orberyllium copper pins manually installed in a printed circuit board. Thepitch of the probe pins of a cantilever type probe card is about 50 μm.The pitch of the probe pins of a vertical type probe card is about 100μm. Due to technical limitations, the pitch of the probe pins of eithertype of probe cards cannot be reduced as desired to fit measuringrequirements for nanoelectronics. Further, because probe pins areinstalled in a printed circuit board manually, the manufacturing cost isrelatively increased with the increasing of pin counts. This drawbackcauses the aforesaid conventional probe cards unable to meet futuredemand.

U.S. Pat. No. 6,232,706 discloses a field emission device having bundlesof aligned parallel carbon nanotubes on a substrate. The carbonnanotubes are oriented perpendicular to the substrate. The bundles ofcarbon nanotubes extend only from regions of the substrate patternedwith a catalyst material. The substrate is porous silicon. Thefabrication of the field emission device starts with forming a porouslayer on a silicon substrate by electrochemical etching. Then, a thinlayer of iron is deposited on the porous layer in patterned regions. Theiron is then oxidized into iron oxide, and then the substrate is exposedto ethylene gas at elevated temperature. The iron oxide catalyzes theformation of bundles of aligned parallel carbon nanotubes, which growperpendicular to the substrate surface.

The advantages of U.S. Pat. No. 6,232,706 include (1) small nanotubepitch, and (2) manufacturing cost of nanotubes being not determinedsubject to the pin counts. However, this design still has drawbacks.Because nanotubes are not linked to one another, the whole structure isbulky, resulting in low physical and electrical properties of nanotubes.Further, due to low impact strength of carbon material, nanotubes tendto be broken when pressed by an external object. Due to the aforesaiddrawbacks, nanotubes made according to U.S. Pat. No. 6,232,706 are notsuitable for use as probe pins in a probe card.

Further, U.S. Pat. No. 5,903,161 discloses an electrically conductiverod-shaped single crystal product, which is a rod-shaped single crystalformed by a vapor-liquid-solid method or such a rod-shaped singlecrystal having its forward end alloy portion removed, and the surface ofthe rod-shaped single crystal is coated by an electrically conductivefilm. However, this rod-shaped single crystal product has a low electricconductivity due to its limited electric conducting area.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances inview. It is therefore the main object of the present invention toprovide a compound probe pin, which has good physical properties as wellas good electrical properties. To achieve this object, the compoundprobe pin comprises a bundle of aligned parallel nanotubes/nanorods, anda bonding material bonded to the bundle of aligned parallelnanotubes/nanorods and filled in gaps in the nanotubes/nanorods.

It is another object of the present invention to provide a probe cardhaving integrated compound nano probe pins, which has a small probe pinpitch and is inexpensive to manufacture. To achieve this object, theprobe card comprises a substrate layer having a front side and a backside, and compound probe pins arranged in the substrate layer. Eachcompound probe pin is comprised of a bundle of aligned parallelnanotubes/nanorods, and a bonding material bonded to the bundle ofaligned parallel nanotubes/nanorods and filled in gaps in thenanotubes/nanorods. Each compound probe pin has a base end exposed tothe outside of the back side of the substrate layer, and a distal endspaced above the front side of the substrate layer.

It is still another object of the present invention to provide a probecard fabrication method, which minimizes the pitch of probe pins,improves the physical and electrical properties of probe pins, andincreases pin accounts without increasing much manufacturing cost. Toachieve this object, the probe card fabrication method comprises thesteps of (1) preparing a substrate having a porous surface; (2) coveringa catalyst material on the porous surface of the substrate subject to apredetermined pattern, so as to form a plurality of catalyst strips onthe porous surface of the substrate, the catalyst strips each comprisinga plurality of catalyst elements; (3) exposing the catalyst strips to anenvironment containing a predetermined gas and having a temperatureabove room temperature, for enabling the catalyst elements to react withthe gas so as to form bundles of aligned parallel nanotubes/nanorods atthe catalyst strips; and (4) covering the bundles of aligned parallelnanotubes/nanorods by a bonding material, enabling the bonding materialto pass into gaps in the aligned parallel nanotubes/nanorods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a finished product obtained after step (1)of the probe card fabrication method according to the present invention.

FIG. 2 is a top view of a finished product obtained after step (2) ofthe probe card fabrication method according to the present invention.

FIG. 3 is a sectional view of a finished product obtained after step (3)of the probe card fabrication method according to the present invention.

FIG. 4 is a sectional view of a finished product obtained after step (4)of the probe card fabrication method according to the present invention.

FIG. 5 is an enlarged view of part A of FIG. 4.

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5.

FIG. 7 is a sectional view of a finished product obtained after step (5)of the probe card fabrication method according to the present invention.

FIG. 8 is a sectional view of a finished product obtained after step (6)of the probe card fabrication method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1˜4, a probe card fabrication method includes thesteps of:

(1) Prepare a p-doped n+-type si(100) substrate 10, then usehydrofluoric acid solution and platinum served as a cathode toelectrochemically etch one surface 11 of the substrate 10, forming pores12 in the surface 11, each pore 12 having a diameter below 3 nm, asshown in FIG. 1.

(2) Use lithography and evaporation techniques to cover a catalystmaterial, for example, iron (Fe), on the surface 11, forming a matrix ofcatalyst strips 20 on the surface 11, each catalyst strips 20 havingdensely arranged fine catalyst elements 21, as shown in FIG. 2.

(3) Put the substrate 10 in a CVD (chemical vapor deposition) stovepipe, then increase the temperature in the stove pipe properly andsupply a carbon-contained gas, for example, C₂H₂, causing the catalystelements 21 to make a chemical reaction with the supplied gas, so thatbundles 30 of aligned parallel carbon nanotubes 31 are crystallized andrespectively formed in the catalyst strips 20 and extended in directionsubstantially perpendicular to the surface 11 of the substrate 10, asshown in FIG. 3.

(4) Cover the bundles 30 by a bonding material, for enabling the appliedbonding material to pass into gaps in carbon nanotubes 31. According tothis embodiment, a metal material of good electrical properties andmechanical properties, for example, copper 40 is covered on the bundles30 by electroplating, enabling copper 40 to pass into gaps in carbonnanotubes 31 of each bundle 30, forming compound probe pins 50 on thesubstrate 10, as shown in FIG. 4.

With reference to FIGS. 5 and 6, the compound probe pin 50 made subjectto the aforesaid method comprises a bundle 30 of substantially alignedparallel carbon nanotubes 31 and a metal material 40 covered on thebundle 30 (see FIG. 5) and filled up the gaps in the carbon nanotubes 31(see FIG. 6). Because the bundle 30 is covered by the metal material 40and the carbon nanotubes 31 are fixedly fastened to one another by themetal material 40, the compound probe pin 50 has a dense structure, andgood mechanical, physical and electrical properties.

After the aforesaid four steps, each compound probe pin 50 has a baseend and a distal end. The base end is fixedly connected to the surface11 of the substrate 10 by one catalyst strip 20.

With reference to FIGS. 7 and 8, after the aforesaid four steps, itproceeds to the following steps:

(5) Apply a layer of liquid epoxy resin to the surface 11 of thesubstrate 10, enabling the layer of liquid epoxy resin to cover the baseends of the compound probe pins 50 and to form a substrate layer 60 whenhardened as shown in FIG. 7.

(6) Remove the substrate 10 from the substrate layer 60. At this time,the substrate layer 60 has a front side 61 and a back side 62, the baseends of the compound nano probe pins 50 are exposed out of the back side62 of the substrate layer 60, and the distal ends of the compound nanoprobe pins 50 are spaced above the front side 61 of the substrate layer60. A metal conducting block 70 is then respectively formed in theexposed base end of each compound nano probe pin 50 for connectioneither directly or indirectly to a printed circuit board, forming aprobe card.

As indicated above, the invention uses nanotechnology to form multiplecompound probe pins at a time, so that the pitch of probe pins can begreatly reduced. A probe card made according to the present invention issuitable for measuring electrical properties of nanoelectronic elements.Because multiple compound probe pins are formed at a time, it breaks thelimitation that the manufacturing cost is directly proportional to pincounts, and the manufacturing cost is greatly lowered. Because compoundprobe pins made according to the present invention have a goodstructure, they provide good mechanical, physical and electricalproperties.

In the aforesaid fabrication procedure, iron (Fe) and C₂H₂ arerespectively used in step (2) and step (3). Other suitable metalmaterials and gases may be used. For example, when gold (Au) is used asa catalyst material, SiCl₄+H₂ is supplied to the stove pipe, causingformation of bundles of aligned parallel silicon nanorods, which growperpendicular to the substrate surface.

Further, arc-discharge or laser evaporation may be used to substitutefor chemical vapor deposition.

The material for bonding nanotubes/nanorods can be selected from gold,nickel, nickel alloy, silver, tungsten alloy, copper, or beryllium.Because carbon nanotubes have good electric conductivity, insulatingmaterial, for example, rubber may be used and covered on the peripheryof each bundle of carbon nanotubes, leaving the top end of each bundleof carbon nanotubes exposed to the outside for electric connection.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A nano probe pin fabrication method comprising the steps of: (1)preparing a substrate having a porous surface; (2) covering a catalystmaterial on the porous surface of said substrate subject to apredetermined pattern, so as to form a plurality of catalyst strips onthe porous surface of said substrate, said catalyst strips each having aplurality of catalyst elements; (3) exposing said catalyst strips to anenvironment containing a predetermined gas and having a temperatureabove room temperature, for enabling said catalyst elements to reactwith said gas so as to form bundles of aligned parallelnanotubes/nanorods at said catalyst strips; and (4) covering saidbundles of aligned parallel nanotubes/nanorods by a bonding material,enabling said bonding material to fill up gaps in between the saidaligned parallel nanotubes/nanorods.
 2. The nano probe pin fabricationmethod as claimed in claim 1, wherein said substrate having a poroussurface prepared during said step (1) is obtained by preparing a p-dopedn+-type si (100) substrate, and then using hydrofluoric acid solutionand platinum served as a cathode to electrochemically etch one surfaceof said p-doped n+-type si (100) substrate, forming pores in the surfaceof said p-doped n+-type si (100) substrate, said pores having diametersbelow 3 nm.
 3. The nano probe pin fabrication method as claimed in claim1, wherein the catalyst material used in said step (2) is iron (Fe), andthe gas used in said step (3) is C₂H₂.
 4. The nano probe pin fabricationmethod as claimed in claim 3, wherein said catalyst material is coveredon the porous surface of said substrate by lithography and evaporationin the form of a matrix.
 5. The nano probe pin fabrication method asclaimed in claim 1, wherein said step (3) is achieved by putting saidsubstrate in a CVD (chemical vapor deposition) stove pipe, and thensupplying C₂H₂ to said CVD stove pipe when increasing the temperature insaid CVD stove pipe, for enabling said catalyst elements to make achemical reaction with C₂H₂, so that bundles of aligned parallel carbonnanotubes are crystallized and respectively formed at said catalyststrips and extended in a direction substantially perpendicular to theporous surface of said substrate.
 6. The nano probe pin fabricationmethod as claimed in claim 1, wherein said bonding material used duringstep (4) is a metal material.
 7. The nano probe pin fabrication methodas claimed in claim 1, wherein said bonding material used during saidstep (4) is copper.
 8. The nano probe pin fabrication method as claimedin claim 1, wherein said bonding material used during said step (4) isan electrically insulating material.
 9. The nano probe pin fabricationmethod as claimed in claim 1, wherein said bonding material used duringsaid step (4) is rubber.
 10. The nano probe pin fabrication method asclaimed in claim 6, wherein the metal material used for said bondingmaterial during said step (4) is electroplated on said bundles ofaligned parallel nanotubes/nanorods.
 11. The nano probe pin fabricationmethod as claimed in claim 10, wherein the metal covered on said bundlesof aligned parallel nanotubes/nanorods during said step (4) fills upgaps in aligned parallel nanotubes/nanorods of said bundles of alignedparallel nanotubes/nanorods.
 12. The nano probe pin fabrication methodas claimed in claim 9, wherein the rubber used for said bonding materialduring said step (4) is covered on the periphery of said bundles ofaligned parallel nanotubes/nanorods and passed into gaps alignedparallel nanotubes/nanorods of said bundles of aligned parallelnanotubes/nanorods, leaving a top end of each of said bundles of alignedparallel nanotubes/nanorods exposed to the outside for electricconnection.
 13. The nano probe pin fabrication method as claimed inclaim 1 further comprising the step of: (5) applying a layer of liquidepoxy resin to the porous surface of said substrate, enabling said layerof liquid epoxy resin to cover base ends of said bundles of alignedparallel nanotubes/nanorods and to form a substrate layer when hardened,and (6) removing said substrate from said substrate layer such that thebase end of each of the bundles of nanotubes/nanorods is exposed on aback side of said substrate layer, and then forming a respective metalconducting block on the exposed base end of each of the bundles ofnanotubes/nanorods.
 14. The nano probe pin fabrication method as claimedin claim 1 wherein said step (3) is achieved by arc-discharge or laserevaporation.
 15. The nano probe pin fabrication method as claimed inclaim 1 wherein the material for bonding nanotubes/nanorods is selectedfrom gold, nickel, nickel alloy, silver, tungsten alloy, copper orberyllium.
 16. The nano probe pin fabrication method as claimed in claim1, wherein the catalyst material used in said step (2) is gold (Au), andthe gas used in said step (3) is SiCl₄+H₂.
 17. A nano probe pinfabrication method comprising the steps of: (1) preparing a substratehaving a porous surface; (2) covering a catalyst material on the poroussurface of said substrate subject to a predetermined pattern, so as toform a plurality of catalyst strips on the porous surface of saidsubstrate, said catalyst strips each having a plurality of catalystelements; (3) exposing said catalyst strips to an environment containinga predetermined gas and having a temperature above room temperature, forenabling said catalyst elements to react with said gas so as to formbundles of aligned parallel nanotubes/nanorods at said catalyst strips;and (4) covering said bundles of aligned parallel nanotubes/nanorods bya bonding material, enabling said bonding material to fill up gaps inbetween the said aligned parallel nanotubes/nanorods wherein a rubberused for said bonding material during said step (4) is covered on theperiphery of said bundles of aligned parallel nanotubes/nanorods andpassed into gaps aligned parallel nanotubes/nanorods of said bundles ofaligned parallel nanotubes/nanorods, leaving a top end of each of saidbundles of aligned parallel nanotubes/nanorods exposed to the outsidefor electric connection.